README.md

Follow the documentation here. In your pubspec don't forget to add assets property. My folder structure is

• /
  • bin
    • env_testing
      • env_testing.dart
  • env
    • dev.env
    • stag.env

So the path in assets would be

...
assets:
  - env/dev.env
  - env/stag.env

env_testing.dart

import 'dart:io';

import 'package:dotenv/dotenv.dart';

void main() {
  final env = DotEnv(includePlatformEnvironment: false)..load(['env/stag.env']);
  print(env['BASE_API']);
  exit(0);
}